Interpretive Summary: Hydrangea and Schizophragma genera (Hydrangeaceae) are popular ornamental plants. Hydrangea anomala subsp. petiolaris (Siebold & Zucc.) E. M. McClint and S. hydrangeoides Sieb. & Zucc are both deciduous shrubs that climb using rootlets. Both are native to Japan, Korea, and China. The leaf morphologies of these two species are somewhat similar. Hydrangea anomala subsp. petiolaris and Schizophragma hydrangeoides plants were growing sympatrically in Jeju, Korea, but one group of plants showed different leaf morphology than others. The objectives of this study were to determine whether the unknown accessions from Jeju are intergeneric hybrids by comparing with other Hydrangea anomala and S. hydrangeoides accessions using molecular markers. Based on the RAPD, SNPs, and vegetative morphological characteristics, the unknown accessions were identified as H. anomala var. petiolaris.

Technical Abstract:
This study was designed to identify four unknown accessions of Hydrangeaceae that have leaf morphological characters different from H. anomala var. petiolaris (Siebold & Zucc.) E. M. McClint and Schizophragma hydrangeoides Sieb. & Zucc. but were growing adjacent to both species in Jeju, Korea. A total of 29 accessions of Hydrangea and Schizophragma from the wild were collected and analyzed using randomly amplified polymorphic DNA (RAPD) and single nucleotide polymorphisms (SNPs) from the ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit (rbcL) gene. Morphological characteristics of leaves and shoot apices of several accessions were also examined. Based on the RAPD, SNPs, and vegetative morphological characteristics, the unknown accessions were identified as H. anomala var. petiolaris. Schizophragma hydrangeoides collected from Ulleung Island, Korea clustered together with those collected from Japan, showing the geographic proximity of these two populations. The RAPD markers and SNP analysis effectively identified all four unknown accessions.